Conventional inkjet printers print on recording paper by ejecting ink from a print head having a plurality of ink ejection openings or nozzles formed therein. In this inkjet printer, ink ejection problems can occur when air bubbles are generated in the ink while the print head is in use, when ink or microparticles of foreign matter are deposited on the surface of the ink ejection openings, and the like. Further, if the printer is left unused for a long period of time, the ink ejection openings may become clogged with ink, leading to ink ejection problems. Since printing quality suffers if a printing operation is performed while ink ejection is problematic, a purge process is generally performed to restore the ink ejection openings to a good ejection state. The purge process is performed, for example, by generating a negative pressure with a pump to draw ink out of the print head after hermetically sealing the print head with a suction cap, or performing a preliminary ejection process to eject ink from the nozzles.
Since the user executes this purge process manually after detecting printing problems, printing complications occur once at the very least. In order to overcome this problem, an inkjet printer such as that disclosed in U.S. Pat. No. 6,386,677B1 has been proposed to execute a purge process automatically when conditions indicating the potential for printing problems have been met. In this inkjet printer, if conditions indicating the potential for printing complications are met, for example, if a prescribed time or more has elapsed since the previous purge process, the inkjet printer executes a purge process before such printing problems can occur, thereby preventing the occurrence of printing complications.